A stack barcode is a kind of barcode materialized by way of stacking one-dimensional barcodes so as to increase the amount of information; and as a typical stack barcode, there is PDF417.
There are proposed various kinds of barcode readers; in which a stack barcode is captured into a digital image by means of an optical method, and the stack barcode in the image is analyzed by means of an image processing method in order to read out a datum recorded (for example, refer to Patent Document 1).
PDF417 (stack barcode) described in Patent Document 1 is provided with an error correction function. The greater number of error-correction code-words PDF417 includes in it, the more error corrections an error correction capability is able to make.
Accordingly, a stack barcode reader described in Patent Document 1 is provided with a decoded result selection unit, for selecting a decoded result having a less number of error corrections. In other words, even in a decoded result, there is a variation in reliability with respect to measured width of a bar and a space; and therefore, in the stack barcode reader, an arrangement is made so as to quantitatively evaluate the variation for a higher level of decoding process.